The present invention relates to an annular gap seal for a valve, which may block while in a blocked position the flow of a fluid from a high-pressure side to a low-pressure side of the valve, the valve having a cylinder which the fluid may flow through and in which a piston is axially displaceable, and an annular gap between the piston and the cylinder being sealable in the blocked position using the annular gap seal, which lies in a groove around the circumference of the cylinder.
Annular gap seals of this type for valves are generally known. German patent DE 37 31 349 A1 discloses a trapezoidal annular gap seal, for example, lying in a trapezoidal groove and which may be placed under a pre-tension using a lock washer. German patent DE 29 29 389 A1 discloses a regulating valve, in which an annular gap seal of this type is typically used.
The known annular gap seals have leakage flows in the blocked position, which are tolerated less and less for reasons of quality assurance in industrial production and control processes. The causes of these leakage flows are (1) the occurrence of wear and aging on the seal elements, (2) insufficient radial adjustment capability of the known annular gap seals and (3) inadequate consistency of their material properties upon changes of the operating temperature.
In addition, the known annular gap seals—precisely because of the leakage flows—are only capable of securing facility parts from backflows in a very limited way.